docs: update the ethernet diagram
docs: update the ethernet diagram

The new version removes the VM to focus more on vpnkit. The diagram
adds the SOCK_{STREAM,DGRAM} connections from the TCP/IP endpoints.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@docker.com>

djs55/vpnkit,djs55/vpnkit,djs55/vpnkit